Parallel straight edge



June 13, w39- A. F. LINSNER PARALLEL STRAIGHT EDGE Filed March 25, 1938Patented June 13, 1939 UNHTED STATES PATENT oFFlcE PARALLEL STRAIGHT EDGE Application March 23, 1938, Serial No. 197,570

s claims.`

This invention relates to a parallel straight edge.

An object of the invention resides in the provision of a parallelstraight edge wherein the eni tire upper surface of the instrument isunobstructed so that it will present the minimum interference to thedraftsman.

It is a further object of the invention to so construct the device thatthe minimum friction between the instrument and the drawing board orpaper will be present.

As a further object, the invention seeks to provide a simplifiedconstruction attaining the above objects and which may be moved acrossthe drafting paper with the minimum exertion and without necessitatingthe application of pressure by both hands of the draftsman.

A further object of the invention resides in the provision of means forlocking the device in a definite position on the drawing board.

In the drawing I have illustrated an embodiment of my invention but itis to be understood that I am not to be limited to the details ofconstruction therein shown except insofar as this g limitation isnecessitated by the claims.

' In the drawing:

Figure 1 is a plan view of the device showing the same located upon adrawing board, the drawing board being broken away for the sake ofconvenience;

Figure 2 is a sectional view on line 2--2 of Figure 1;

Figure 3 is a sectional View on line 3 3 of Figure 2;

for securing the guide cord to the board.

Figure 5 is a detail of one of the guide pulleys that is attached to onecorner of the board;

Figure 6 is a detail of the means for securing the guide cord at onecorner of the board;

Figure 7 is a detail ofthe means for securing the guide cord to theother corner of the board;

Figure 8 is a detail of a modification disclosing a lock for securingthe straight edge in a denite position on the board; and

Figure 9 is a sectional view disclosing the position of the lock in thestraight edge,

Referring now to the drawing wherein like reference characters indicatelike parts, the straight edge consists of a relatively flat elongatedbody portion I having ruling edges 2, the body portion and the edgesbeing made of the desired material.

A double pulley 3 is mounted on a shaft 4 for rotation, `there beingball bearings interposed Figure 4 is a detailed sectional View of thelock between the pulley and the shaft. The shaft is made, preferably, oftwo parts as indicated in Figure 2, one of which, 6, is in screwthreaded engagement with a bracket I and the other of which, 8, acts asa locking nut to secure the shaft 6 element 6 to the bracket 1.

This bracket I is attached to the upper face of one end of the bodyportion I of the straight edge.

A similar pulley 9 is attached to the other end 10 of the body portion Iof the straight edge in a similar manner.

The body portion of the straight edge is provided with a longitudinallyextending channel ID that is laterally relatively wide, which results lin the reduction of the surface contact between the lower face of thestraight edge and the paper and consequently, in the reduction of fric.-tion between the two. AIn other words, this channel I9 reduces theextent of the lower surface I I of the straight edge and consequentlyreduces the area of surface contact between the lower surface of thebody of the straight edge and the drafting paper. This channel Ir isclosed at its ends, as at IIII so that it forms, in effect, when thestraight edge is in Contact with the paper, a chamber.

At the ends of the straight edge longitudinal elongated openings I2, I3,I4 and I5 extend through the body of the straight edge and establishcommunication between the channel II) and the upper face of the straightedge adjacent the pulleys 3 and 9 and permit the guide cord to extendthrough the straight edge from the supper surface to the channel.

At two of t'he corners of the drawing board It, pulleys Il and I8 areattached, these pulleys being carried by brackets I9 which are attachedto the drawing board by screws and which carry prongs 2| that penetratethe edge of the board to maintain the pivot on which the pulleys rotateat right angles to the upper surface of the board.

At one of the opposite corners of the board, a bracket 22 is attachedwhich bracket is disclosed clearly in Figure 6 of the drawing and whichis provided with an opening 23. This bracket is formed of two parts, oneof which, 24, is directly attached to the board and the other of which,25, is pivoted 29 on the part 24. At the remaining corner of the board asimilar bracket 2l is attached to the edge of the board but this bracketis provided with a key hole slot 28.

The guide cord 29 in being placed is inserted through the opening 23 ofthe bracket 22 and knotted as at 30 to maintain this end of the guidecord in engagement with the bracket. The cord then passes around thepulley 3 and through the opening I2 in the body of the straight edge. Itthen passes through the opening I5 and around the opposite side of thepulley 9 and then around the pulley I1. From the pulley I'I the cordextends to and around the pulley I8 and then again around the doublepulley 3 through the opening I3 and, crossing itself, through theopening I4 and around the double pulley 9. Its end is then inserted inthe key hole slot 21. By means of this end 3| the cord may be pulledtaut and then engaged in the reduced end of the key hole slot 28 tomaintain it in this condition.

In order that the cord 29 may be secured in relation to the board I haveprovided a clamp disclosed in Figure 4, which includes spring jaws 32and a cam 33, for forcing the jaws together. This clamp is attached tothe board by suitable means such as a screw 34 and through the clamp thecord 29 passes. Thus, after the straight edge has been adjusted into theposition that it is desired that it should occupy, the clamp may beactuated to insure the maintaining of the cord stationary with theconsequent travel of the straight edge in parallelism.

It will be realized that with this construction, when the straight edgeis set in its proper position with its edge either horizontal or inangular relation to the board and the clamp disclosed in Figure 4 in itsclamping condition, the straight edge may be moved .across the board sothat its leading edge will be always parallel with the positions that itpreviously occupied. In other Words, if the straight edge is set so thathorizontal lines may be ruled as it is moved from position to position,each succeeding line will be parallel with the preceding one, or if itis set for the ruling of angular lines, such as cross hatching, eachsucceeding line will, nevertheless, be parallel with the preceding ones.When the clamp shown in Figure 4 is loosened the straight edge, ofcourse, may be shifted to any of the other desired positions.

In Figures 8 and 9 of the drawing I have disclosed a modication of theinvention. This includes a locking cam 35 that is provided with anactuating handle 36. The cam 35 is located within the channel I and theactuating handle 36 on the upper surface of the body of the straightedge. The two reaches of the cord 29 that pass through the channel I0 ofthe body of the straight edge pass between one wall of the channel IIIand the cam 35 so that when the cam is actuated these reaches of thecord are locked between the cam and the wall. The purpose of thislocking is to maintain the straight edge in any given position, or inother words, to prevent its being shifted across the board, in whichevent it may be used as a base for other ruling instruments.

Of course were there no means for escape of the air from the channel I0there would be a tendency to set up a suction as the straight edge ismoved across the paper and this would interfere with the free movement.However, the provisions of the openings I2, I3, I4, and I which serve topermit the guide cord to pass from the upper to the lower surface of thestraight edge insures the escape of the air from the channel and thedestruction of the suction with the consequent ease of movement of thestraight edge.

It will be realized that certain modifications in the details ofconstruction that I have above described may be made without departingfrom the spirit of the invention or existing scope of the claims.

I claim:

1. A parallel straight edge including an elongated relatively thin bodyportion having a relatively wide longitudinal channel in the lower facethereof and closed at its ends; a pulley carried by each end of thestraight edge adjacent and above its upper face and said body portionhaving .a pair of slots adjacent each pulley and establishingcommunication between the channel and the pulley through the upper faceof the straight edge.

2. A parallel straight edge including an elongated relatively thin bodyportion having on its lower face a relatively wide longitudinal channelto reduce friction as the straight edge is moved, a pulley carried byeach end of the straight edge and substantially in the plane of theupper face, said upper face having slots therein adjacent the pulleys,and cords passing about the pulleys and through the slots to saidlongitudinal channel.

3. A straight edge of the character set forth in claim 2, in which alocking device for the cords is located within said channel.

ARTHUR F. LINSNER.

